Air Testing – Which and How Many


It is important to remember that unless you are building a Passivhaus, the main driver for air testing comes from DEAP BER Calculations.


Small schemes are those including 3 dwellings or less. In this case if it can be demonstrated that during the preceding 12 month period, a dwelling of the same type constructed by the same builder was tested and satisfied the criterion set in paragraph 1.2.4.4 of Part L.


For a dwelling which is a borderline pass, this may be enough to cause a BER failure, and so the client in this case may choose to test that unit and secure a better result.

The regulations around air testing can appear complex – some dwellings need testing, yet some do not. One dwelling may also require a better result than another. Here we can hopefully offer some simple guidance.
Which Regs?

The procedure and method for air testing dwellings is set by:

  • Guidance set within Part L3 (latest version 2011)
  • Updates to DEAP conventions
  • Testing standards set by NSAI and ATTMA (The Air Tightness Testing and Measurement Association) and I.S. EN 13829:200

It is important to remember that unless you are building a Passivhaus, the main driver for air testing comes from DEAP BER Calculations. DEAP calculations measure the energy performance of the dwelling, and one key aspect of that calculation is the air tightness of the dwelling
– i.e how much air is leaking out through gaps and cracks in the fabric. Without an air permeability figure, DEAP BER calculations cannot be completed, and without DEAP calcs, air testing is pretty meaningless!

Which Dwellings Do I Need to Test?

This will vary depending on the type of development. General principles are:

    • 1 unit of each dwelling type for 4 or less units
    • 2 units of each dwelling type for between 5 and 40 units
    • At least 5% of units for each dwelling type Tests should be carried out on first 25% constructed of that type

    Alternatives For Small Schemes

    Small schemes are those including 3 dwellings or less. In this case if it can be demonstrated that during the preceding 12 month period, a dwelling of the same type constructed by the same builder was tested and satisfied the criterion set in paragraph 1.2.4.4 of Part L. However, if the assumed air change rate in the calculation of the EPC and CPC using the DEAP methodology is less than the criterion set in paragraph 1.3.4.4, a pressure test to verify this assumed value should be carried out. The guidance given in this sub-section would apply in this situation.

    Untested Units

    If a dwelling is not tested for any of the reasons above:
    Paragraph 1.5.4.7 Where an air permeability value better than the backstop value of 7 m3/hr/m2 at 50 Pascals is claimed for use in DEAP, a test should be performed on each dwelling claiming that value. Therefore any untested dwellings under the BER DEAP regs will effectively take a ‘hit’ which will affect the energy performance of that dwelling.

    For a dwelling which is a borderline pass, this may be enough to cause a BER failure, and so the client in this case may choose to test that unit and secure a better result.

    Failed Tests

    If a dwelling does not meet the required DEAP parameter, remedial works must be carried out and the dwelling re-tested until it complies. It is sometimes possible (depending on your test engineers schedule!) to retest straight away if quick, minor remedial works can be carried out. This may involve caulking or application of sealant for example. Once the test is completed successfully, a further additional dwelling of the same type should be tested, thereby increasing the sample size.

    For further reading why not take a look at:

    Air Permeability Testing – Get Your Building Airtight

    Air Permeability Testing – The Info

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